Influence of grain size on high temperature oxidation behavior of Cr2AlC ceramics

The influence of grain size on the oxidation behavior of Cr2AlC at 1100 °C and 1200 °C for different times was investigated using fine grained (2 μm) and coarse grained (60 μm) samples. The two materials show a good oxidation resistance owing to the formation of a dense and continuous Al2O3 layer. The oxidation rate of the fine grained Cr2AlC is relatively faster than that of the coarse grained Cr2AlC. The microstructure and phase composition of scale was characterized. After oxidation at 1100 °C and 1200 °C for long times up to 100 h, only a dense and continuous α-Al2O3 oxide layer formed on both the fine grained and coarse grained Cr2AlC. However, after oxidation at 1100 °C for a relatively short 2 h period, a Cr7C3 compound was detected beneath the α-Al2O3 oxide layer on the coarse grained Cr2AlC, yet no Cr7C3 was found in the fine grained Cr2AlC. The oxidation mechanism of the fine and the coarse grained Cr2AlC was discussed.